Choices are made within social and cultural contexts. The context within which many people ae now adopting such an identity directly coincides with the promotion of gender identity theory. 'Trans' is a framing device, a narrative that provides an explanation and a solution to personal feelings of distress and discomfort. There have been many other such devices throughout history.
Even back in 2010 when I was last teaching in schools and colleges, there was no such thing as 'a trans child'. Nobody had heard of it.
Social contagions are spread with great ease via social media these days ( the Iphone came in 2014), and there has been an orchestrated and concerted campaign to embed this ideology in all of our institutions. Post modernistic theories of the self promoted and taught on university campuses in the 1980s and 1990s and beyond have borne their fruit.
Stonewall, especially, was responsible for much of this in the UK ( and we have recently discovered how much Stonewall relied on U.S aid dollars) after achieving gay marriage equality they set their sights to 'trans' as the next big campaign. And here we are. The 'trans umbrella' and the whole 'queering' project.